In-vitro study of mouse peritoneal macrophage response to virulent and avirulent strains of mycobacteria.

An immunological study of pathogenesis of tuberculosis was carried out in BALB-c mice in-vitro. Peritoneal macrophages obtained from BALB-c mice were challenged with virulent (H37Rv) and avirulent (H37Ra, BCG, M. phlei) strains of mycobacteria. Activated peritoneal macrophages showed enlargement, presence of intracellular bacteria and vacuolation. These significant changes in macrophage morphology were clearly evidenced in cells infected with virulent strains of Mycobacterium tuberculosis i.e. H37Rv while being absent in cells infected with avirulent H37Ra, BCG and M. phlei. Virulent mycobacteria (H37Rv) survive the phagocytic action of macrophages by residing inside the vacuoles. The capacity of virulent and avirulent strain to stimulate TNF-alpha production from peritoneal macrophage of BALB-c mice was also examined at different time interval i.e. 1,2,4,6 and 8th day by measuring cytolytic activity of culture supernatant against murine fibroblast cell line. The pattern of highest TNF release was in case of H37Rv and least with M. phlei as measured in culture supernatant after 1,2,4,6 and 8th day.

Non acid-fast fluorescent M. leprae (?) in skin smears from leprosy patients.

Smears from 74 known smear negative cases of leprosy were examined after staining with Auramine 'O'. 40.54% cases were positive for fluorescent bacilli. 60.52% of cases on treatment and 19.44% cases after RFT had fluorescent bacilli in the skin smears. Results suggest the possibility of a non acid-fast fluorescent positive variant of M. leprae.

BI of patient vs BI of individual sites.

An analysis of 200 skin smear results from multibacillary patients showed that the average bacteriological index (BI) of a patient varied considerably from his site-wise highest BI. The average BI was equal to site wise highest BI only in 17.5% of cases and in the rest, it ranged from 99% to as low as 36% of the highest site-wise BI. In follow-up smears, site-wise consistency of the highest BI was found in 96% of cases. It is suggested that for follow-up purposes, repeating smear from only one such site would be adequate.